If you want to put on fat, a diet rich in sugary drinks will do you wonders. Doesn't have to be expensive fruit juice either. Just drink lots of soft drinks every day, like, 3 litres or more, and you're setting yourself on a solid path to obesity.

If you want to put on muscle you'll need to do better than that.

There's always GOMAD! https://stronglifts.com/gomad-milk-squats-gallon-gain-weight...

Yep, then spend 2 years in pain from the tendonitis and ligament damage. Those tissue have a lot less blood flow than muscle so they can't keep up with stupid fast growth. Good form to prevent injury takes practice too, years of it! But I suppose if you are taking steroids you might heal faster in the short term.

Or just gain a pound a month and talk to a therapist about your body dysmorphia. A therapist is way cheaper than a surgeon. You'll also learn a lot about the limits of your body and learn a sustainable way to build strength and muscle.

Hah remember it well when I was trying to get to 20 stone.

Nope. Fruit juice is mostly water. Even raw sugar is only 380 kcal/g, just a bit more than French fries (310 kcal/g).

If you're underweight, you should eat food.

Something about your numbers seem way, way off (by two orders of magnitude, actually). Could you explain better or point to references?

I think it's per 100g, not per g.

Edit: yeah. That's how dietary references are done lots of non-US places. https://www.wolframalpha.com/input/?i=calories+in+100g+of+su...

As one of the weird perpetually hungry, healthy appetite, fairly skinny person I've been told that peanut butter is among one of the better options for maximizing caloric intake. I should be eating nearly a cup of peanut butter per day it seems and the same calories would be in 8 smoothies or so.